Residuum conversion process



July 15, 1958 A. w. LANGER, JR., ETAL 2,84

RESIDUUM CONVERSION PROCESS Filed Aug. 20, 1954 2 Sheets-Sheet 1 H 9.2256mm l A A m5 mo mozzwwo 1 .EEEE t A 3 ANN J6 m I\ U 36 Al @zEfiIzmoOmo I mmw w All. PIQJ o ARTHUR w. LANGERJn INVENTORS GRAHAM e.WANLESS CARL s. CARLSON BY WmMA MAAM ATTORNEY$ July 15, 1958 Filed Aug.20, 1954 HYDROGENATOR A. w. LANGER, JR., EIAL 2,843,530

RESIDUUM CONVERSION PROCESS 2 Sheets-Sheet 2 LIGHT GASES 6 NAPHTHAS 1 7HEATING THERMAL TAR - BLEED RESIDUUM REACT STEAM ARTHUR W. LANGER, JrINVENTORS GRAHAM G. WANLESS CARL S. CARLSON BYMJM 6. 7t. ATTORNEYSUnited States Patent RESIDIJUM convnnsroN rnocnss Arthur W. Longer, in,Nixon, and Graham G. Wanless, Wcstiield, N. .l., and Carl .5. Carlson,Crystal Lake, ilk, assignors to Esso Research and Engineering \Company,a corporation of Delaware Application August 20, 1954, Serial No.451,254

4 Claims. (Cl. 1%.-S0)

This invention pertains to the converting of hydrocarbon oils byhydrogenolysis. More particularly it is concerned with the upgrading ofpetroleum oils, particularly heavy high boiling oils such as vacuumresidua by thermal cracking of the oil in the presence of a hydrogendonor diluent. By the process of this invention, low value hydrogendeficient oils having coke forming propensities during thermal crackingare converted to more volatile products such as light distillates foruse as motor fuels and gas oils suitable as feed stocks for catalyticcracking processes. i

A process termed hydrogen donor diluent cracking (I-IDDC) has recentlybeen proposed. In this process, a heavy, low value oil is upgraded byadmixing it with a hydrogen donor diluent material, aromatic-naphthenicin nature, and thermally cracking the mixture as' in a thermal crackingcoil. The hydrogen donor diluent is a polycyclic condensed ring aromaticor an aromaticnaphthenic material that has been especially prepared bypartial hydrogenation from selected normally surplusage, refinerystreams such as catalytic cycle stocks, thermal tars, etc. The hydrogendonor diluent used has the ability to take up hydrogen in thehydrogenation zone and readily release it to hydrogen deficient oil in athermal cracking zone. In this manner of hydrocracking oils, the oilbeing upgraded, usually a residual oil, is not contacted directly withthe hydrogenation catalyst and does not, therefore, impair the activityof the catalyst by contamination. The amount of concomitant light gasesand coke produced by this process is relatively small, usually being inthe order of about 5 to This technique of HDDC is more fuly presented byco-pending and now abandoned application entitled, Upgrading of HeavyHydrocarbon Oils, Serial No. 365,335, filed July 1, 1953, by Langer, aco-inventor of the present invention.

In the above-described HDDC processwherein the products, unconvertedfeed and spent diluent are continuously removed from the reactor as anequilibrium mixture, in order to obtain high conversions, it has beennecessary to separate and recycle unconverted materials from thereaction mixture. Further, it has been necessary to use a high hydrogendonor diluent to residuum ratio to prevent coking in the reactor and tosecure reasonable conversions. The present invention proposes a novelmethod of hydrogen donor diluent cracking that overcomes thesedisadvantages.

According to the present invention, a hydrogen donor diluent is admixedwith a hydrogen deficient oil and the resulting mixture is subjected toliquid phase thermal cracking. During the thermal cracking theconversion products are continuously removed overhead as vapors. Thispractice greatly increases the ratio of hydrogen donor diluent tounconverted material in the liquid phase. Consequently, coke depositionis greatly minimized or eliminated and a much more eificient use is madeof the hydrogen donor diluent than has been made in previously proiceposed processes. In the previous processes, the spent hydrogen donordiluent and the conversion products, along with unconverted material,have been removed from the reactor as an equilibrium mixture of liquidand gases. The withdrawn materials were then separated to obtain thespent hydrogen donor diluent which was partially hydrogenated andrecycled, and the unconverted refractory constituents of the feed, whichwere also recycled to obtain high conversions. Thus, in the past,maximum use has not been made of reactor capacity. The hydrogen donordiluent has been used inefficiently because of its low concentration andvariations in product selectivities were dificult to obtain.

While the main feature of the present invention is a continuous vaporphase withdrawal of the conversion products, other subsidiary featuresand advantages of this invention are to be appreciated. Preferably thespent hydrogen donor diluent is withdrawn from the reactor as a liquidand is preferably separated in a common separation system, e. g., afractionator, with the conversion products to obtain the spent diluentfor hydrogenation. As an alternative, the spent diluent or a portionthereof may also be removed overhead from the reactor as a vapor.Another alternative is to separate the spent diluent, when it iswithdrawn as a liquid, from the unconverted bottoms in a separateseparation system. A third alternative is that when the spent diluent isremoved as a vapor from the reactor, rather than separatelyhydrogenating the diluent, the total overhead along with the diluent maybe partially hydrogenated before separation, thereby regenerating thehydrogen donor diluent.

It is an object of this invention to convert hydrocarbonaceousmaterials, particularly petroleum residua to lighter and more valuabledistillates. Another object is to propose a hydrogen donor diluentcracking process characterized by continuous vapor phase withdrawal ofthe conversion products.

These and other objects and advantages will become apparent as thisdescription proceeds and the attached drawings, forming a part of thespecification, are described in detail.

In the drawings,

Figure I diagrammatically depicts a preferred embodiment of thisinvention adapted to the conversion of a petroleum residuum.

Figure II portrays the modification of the process of this invention inwhich the thermal cracking reactor and the product separation system areintegral.

Charging stocks for the present invention are preferably hydrogendeficient petroleum derived oils, such as crude oils, distillate andresidual fractions therefrom or mixtures thereof. Particularly preferredcharging stocks are heavy residual oils characterized by API gravitiesof 5 to 20, Conradson carbons of 5 to 50 wt. per-cent, and initialboiling points above 850 to 1100 F. This invention is, however, capableof enjoying broader applications. Thus, coal tars, shale oils, tars,asphalts, etc. may also be processed by the present invention. It hasalso been proposed to utilize the HDDC process to extract andconcurrently convert oils from shales and sands. As will hereinafterappear, the present invention also has utility in processing suchhydrocarbonaceous materials.

The sources of the aromatic-naphthenic oil that is partiallyhydrogenated to secure the hydrogen donor diluent have previously beendescribed. In particular, it has been found that the thermal tarsobtained by the thermal cracking of catalytic cycle stocks yieldexcellent donor diluents. It has also been found, however, that certainlube oil extracts, extracts of catalytic cycle stocks, heavy cyclestocks themselves, or bottoms from catalytic cracking can serve as asource of the donor diluent. In any case,

the prime consideration for the selection of a hydrogen donor diluent isthat the diluent should be composed of predominate proportions ofaromatic-naphthenic molecules or condensed ring structures having theability to take up hydrogen in a hydrogenation zone and release it in athermal cracking Zone. Such condensed ring structures are relativelyrefractory and will pass through the thermal cracking zone relativelyunaltered. The condensed ring structures are susceptible to beingrecovered from the reaction mixture and being regenerated by partialhydrogenation. However, while a major proportion of the donor diluentmaterial can be continuously reused, there will normally be some loss ofthe donor diluent and this loss is made up from extraneous sources.

For convenience the pertinent operating conditions applicable to thefollowing description of Figure I are summarized in Table I, presentedhereinafter. With particular reference to Figure I, a charging stock,for example, a vacuum residuum, is blended with a hydrogen donor diluentsupplied by line 2. and a small amount of recycled bottoms supplied byline 3. The blend is passed to a furnace 4 by line 1. In the furnace,the blend is heated to a suitable thermal cracking temperature, at apressure suffieient to maintain substantially liquid phase conditions.The heated material is then passed by line 5 to a reactor 6. Each of thestreams can, of course, be heated separately and passed to the reactor,if it be desired.

Conversion products boiling below the initial boiling point of thediluent are removed continuously from the vapor phase of the reactor andsent to a fractionator 8 by line 7. A liquid phase bleed is taken fromthe bottom of the reactor comprising diluent, products boiling above theinitial boiling point of the diluent, and some unconverted refractoryconstituents of the feed. The liquid phase bleed is introduced into thefractionator 8 by line 9 below the point at which the highest boilingdistillate is removed as a side stream. Thus both vapor phase and liquidphase products are separated in a single fractionator.

Light gases are removed from the fractionator by line 10. Naphthas areremoved by line 11 and heating oils are removed by line 12. A gas oilwhich contains substantially all of the spent donor diluent is removedby line 13. Heavy gas oilsuitable as a catalytic cracking charging stockcan be removed by line 14. The remaining bottoms are removed by line 15,a major portion of which are recycled for further treatment.

Up to about 25% of the spent donor diluent may be bled from the processby line 16. Makeup donor diluent, e. g., thermal tar, is admitted to theprocess by line 17. This makeup thermal tar is necessary in order tomaintain the effectiveness of the diluent to transfer hydrogen. As thethermal cracking occurs, materials not suitable as donors will becracked into the donor diluent boiling range and will reduce theconcentration of the desired condensed ring aromatics, and some of thearomatics will be cracked out of the diluent boiling range. The amountof diluent bled and the amount of diluent makeup depend upon manyfactors, some of which are the diluent boiling range, the width of thediluent boiling range, the amount of hydrogen carried by the diluent,the residuum to diluent ratio, the cracking temperature, and thearomaticity of the residuum.

The spent diluent and the makeup thermal tar is hydrogenated inhydrogenator 18, using conventional methods and using preferably asulfur insensitive catalyst such as nickel tungsten sulfide, cobaltmolybdate, molybdenum sulfide, etc. The hydrogenation conditions are soadjusted that the diluent is only partially hydrogenated. It has beenfound that substantially complete hydrogenation destroys theeffectiveness of the donor diluent. Sutficient hydrogen should be addedto the diluent to make it serve effectively as a hydrogen donor but notto convert it substantially to naphthenes. Hydrogen is supplied to thehydrogenator by line 19 and can originate from any convenient source. Aparticularly suitable source is the hydrogen from hydroformingoperations.

Spent gas is removed from the hydrogenator by line 20, a portion ofwhich may be recycled by line 21. The partially hydrogenated donordiluent is recycled by line 2 to the furnace.

A bleed is provided, by line 15, for the bottoms to prevent build-up ofash contaminants in the system. The amount of the bleed may be as highas 20%, based on fresh feed, but is generally about 1 to 5%. When theprocess is operated to obtain essentially complete residuum elimination,the minimum bottoms bleed is taken consistent with ash removal andremoval of extremely refractory constituents which would eventuallydeposit as coke in the reactor.

The liquid level in the reactor is maintained at 50 to of the reactorcapacity by adjusting pressure, temperature, feed rate, diluent boilingrange and the amount of bleed from the liquid phase. Since the diluentcracks to a much smaller extent than the residuum, it is apparent thatthere is a higher diluent to residuum ratio in the liquid phase of thereactor than in the feed. This results in the most efiicient utilizationof the diluent since it is present in high concentration where it ismost needed, that is, for the liquid phase cracking of the mostrefractory components of the residuum needing a hydrogen donor diluentto prevent coking. For example, consider a feed consisting of 50%residuum and 50% diluent. With only a short contact time about one halfof the residuum cracks readily and is removed from the vapor phase, thusincreasing the diluent to bottoms ratio in the liquid phase from 1 to 1up to 2 to 1.

The range of operating conditions pertinent to this invention aresummarized in Table I. Table '1 also presents a specific example.

Table I Example 1 1,000 F.+ conversion is defined as: vol. percent freshfeed minus v01. percent of products boiling above 1,000 F.

Table II presents an example of the results obtainable by the process ofthis invention when the process is operated in accordance with theexample in Table I, using the particular feed stock indicated.

Table l] Hydrogenated 12.9% West 700/900 F. Inspections Texas ThermalRcsiduum Tar Diluent Elemental analysis, Wt. percent:

C gas, wt. percent 4 C /430" F.,vol. percent 24 430/700 B, vol. percent62 900/ 1000 F., vol. percent 22 Bottoms, bleed, vol. percent 2 Althoughthis process was described using a 700/ 900 F. diluent, it is to beclearly understood that any diluent boiling range may be used in therange of 430 and 1000 F. The main requirement is that the diluentconsist predominantly of condensed ring, aromatic-naphthenic compoundswhich are only partially hydrogenated. For eX- ample, When heavy gas oilis desired for catalytic cracking feed stock the process may be operatedwith a 430/ 650 F. thermal tar diluent. In this case higher pressureswould be used in order to take overhead only 430 F.- products, a largerbleed would be maintained from the liquid phase, and a 650/ 1000 F. gasoil would be separated as the major product. The process using a lowboiling diluent is flexible as gasoline yields can be maximized inpreference to catalytic charging stocks by using a 430/ 650 F. diluentand operating under severe cracking conditions in order to take themajor portion of the products overhead. Another desirable alternativeoperation is obtained by using a diluent boiling in the range 800-1000F. and taking overhead 800 F.-products, thereby maximizing middledistillate yields.

While the present process may be used for the mild thermal treatment ofpetroleum oils in the nature of visbreaking, it is more particularlysuited to the substantially complete conversion of heavy oils. As anexample, however, of a mild severity process, the residual oil can betreated at mild conversions, e. g., 50 to 80% 1000 F. conversions, usinga high bottoms bleed. The bottoms bleed after removal of the spentdiluent can be removed from the process and used as a residual fuel.

With reference to Figure II, a process will be described wherein thedonor diluent is taken overhead as a vapor. As shown, the oil to beupgraded is introduced into the reactor by line 30 wherein it contactsand scrubs an ascending stream of spent diluent and conversion products.It passes downwardly to the base of the reactor and is mixed withsubstantial proportions of the hydrogen donor diluent. The liquidundergoing cracking may be heated by any suitable means. For example, aportion of the liquid can be continuously withdrawn by line 31, passedthrough a heater or furnace 32 and returned to the reactor by line 33.Steam or other substantially inert stripping gas may be admitted to thebase of the reactor by line 34. This steam aids in the recovery of thespent diluent from the liquid.

The conversion products and the spent diluent, after having beenscrubbed by the feed, pass upwardly to the fractionating tower and arecondensed into various product streams. Light gases, naphthas andheating oils are removed by lines 35, 36 and 37, respectively. The spentdonor diluent is removed by line 38 and transferred to a hydrogenator39. A portion of this spent diluent may be cooled and recycled by line40 to effect staged heat re moval in the fractionation column; Asbefore, a portion of this spent diluent stream may be bled from theprocess by line 41 and an equivalent amount of diluent material may beadded to the process by line 42. As an alternative, the condensed ringstructures in the diluent fraction may be concentrated before or afterthe addition of makeup thermal tar by an conventional means such assolvent extraction, thermal cracking, etc.

Hydrogen is admitted to the hydrogenator by line 43. The hydrogenateddonor diluent is removed from the hydrogenator by line 44 andtransferred to the heater 32 wherein it is heated to the reactiontemperature. A bleed amounting to about 1 to 5% of the fresh feed iswithdrawn from the base of the reactor by line 45. This .bleed mayconveniently be adjusted such that the heat requirements of the processare balanced by use of the bleed as a fuel thereby eliminating the needfor external fuel sources.

This particular arrangement having a vapor phase drawoff of the productsand of the spent donor diluent is particularly suited to the processingof a hydrogen-deficient oil on a once-through basis. The residuumcharged to the reactor can be maintained in the reactor until it issubstantially converted to lighter distillates, thus avoiding thenecessity for recycle operation. This arrangement is also suitable forextracting oils from shales, tar sands, etc. The solid material can becharged to the reactor and mixed with the donor diluent and thermallytreated. The conversion products and spent donor diluent can then beremoved overhead, and the spent solid discharged from the bottom of thereactor after being stripped.

While the examples have shown the separation and separate hydrogenationof the spent donor diluent, it is to be appreciated that the totaloverhead from the reactor can be hydrogenated. This alternative mode ofoperation will, however, 'be justified in only a few particularapplications as the consumption of hydrogen will be relatively greater.

Having described the invention, what is sought to be protected byLetters Patent is succinctly set forth in the following claims:

1. A hydrogen donor diluent cracking process which comprises admixing aheavy hydrogen deficient petroleum, oil with 5 to 100 vol. percent ofhydrogen donor diluent comprising partial hydrogenated predominatelyaromaticnaph'thenic hydrocarbons boiling above 430 F., the precursor ofsaid hydrogen donor diluent being selected from the group consisting ofthermal tars, catalytic cycle stocks, extracts thereof, lube oilextracts and mixtures thereof and thermally cracking non-catalyticailyin a thermal cracking zone the mixture at a cracking temperature in therange of 800 to 1100 F. under liquid phase conditions to obtain to 98%1000 F. conversion of said hydrogen deficient oil while continuouslyremoving gasiform conversion products boiling below the boiling range ofsaid diluent, whereby the ratio of unconverted hydrogen donor diluent tounconverted hydrogen deficient oils in the liquid mixture undergoingcracking is substantially increased and efiicient utilization is made ofunconverted hydrogen donor diluent.

2. The hydrogen donor diluent cracking process claimed in claim 1comprising continuously withdrawing liquid from. said thermal crackingzone, separating the liquid to obtain spent hydrogen donor diluent,adding makeup diluent precursor as above described thereto, partiallyhydrogenating a major portion of the separated material including saidmakeup diluent precursor to regenerate the hydrogen donor diluent, andreturning the material so hydrogenated to said thermal cracking zone.

3. The process of claim 2 wherein said gasiform conversion products andwithdrawn liquid are separated in a common fractionation zone to obtainproduct fractions and spent diluent, and recycling a major portion ofthe residue from said fractionation zone to said thermal cracking zonefor further treatment.

4. A process for the conversion of heavy hydrocarbonaceous petroleummaterials which comprises the steps of: introducing a charging stock anda hydrogen donor diluent boiling in a range within the limits of 430 to1000 F. into a thermal cracking zone, maintaining said charging stockand said hydrogen donor diluent therein under liquid phase hydrogendonor diluent, noncatalytic, cracking conditions to obtain relativelylighter vaporous products, continuously withdrawing overhead saidvaporous products, separately withdrawing liquid comprising spentdiluent and unconverted portions of said charging stock from saidthermal cracking zone,

passing the liquid so Withdrawn and said vaporous products to a commonseparation zone, separating therein said spent diluent and addingthereto makeup precursor diluent selected from the group consisting ofthermal tars, catalytic stocks, extracts thereof, lube oil extracts, andmixtures thereof, partially hydrogenating said spent diluent andreturning the material so partially hydrogenated to said thermalcracking zone.

References Cited in the file of this patent UNITED STATES PATENTS HeidSept. 13, 1938 Pier Aug. 17, 1943 Stewart Aug. 7, 1945 GreensfelderSept. 2, 1947 Voge et a1. Apr. 19, 1949

1. A HYDROGEN DONOR DILUENT CRACKING PROCESS WHICH COMPRISES ADMIXING AHEAVY HYDROGEN DEFICIENT PETROLEUM, OIL WITH 5 TO 100 VOL. PERCENT OFHYDROGEN DONOR DILUENT COMPRISING PARTIAL HYDROGENATED PREDOMINATELYAROMATICNAPHTHENIC HYDROCARBONS BOILING ABOVE 430*F., THE PRECURSOR OFSAID HYDROGEN DONOR DILUENT BEING SELECTED FROM THE GROUP CONSISTING OFTHERMAL TARS, CATALYTIC CYCLE STOCKS, EXTRACTS THEREOF, LUBE OILEXTRACTS AND MIXTURES THEREOF AND THERMALLY CRACKING NON-CATALYTICALLYIN A THERMAL CRACKING ZONE THE MIXTURE AT A CRACKING TEMPERATURE IN THERANGE OF 800* TO 1100*F. UNDER LIQUID PHASE CONDITIONS TO OBTAIN 80 TO98% 1000*F. CONVERSION OF SAID HYDROGEN DEFICIENT OIL WHILE CONTINUOUSLYREMOVING GASIFORM CONVERSION PRODUCTS BOILING BELOW THE BOILING RANGE OFSAID DILUENT, WHEREBY THE RATIO OF UNCONVERTED HYDROGEN DONOR DILUENT TOUNCONVERTED HYDROGEN DEFICIENT OILS IN THE LIQUID MIXTURE UNDERGOINGCRACKING IS SUBSTANTIALLY INCREASED AND EFFICIENT UTILIZATION IS MADE OFUNCONVERTED HYDROGEN DONOR DILUENT.